Help with a mask & scroll animation

Hi all,
I’m looking to create an animation like the one linked below, and I’ve been down bad.
https://gordonvonsteiner.com/

It’s going under the ‘Work We’ve Done’ section on my page. I’ve been trying to use a combination of containers as masks to hide content, and overlaying sticky containers to control opacity on certain containers.

One of the things I can’t figure out is how to scroll thru the content in the frame without scrolling the rest of the page behind it. Is there a way to stop a container from sticking at a certain point, instead of waiting for it to scroll out of view?

Anything helps! Thanks guys,
Derek


Here is my public share link:
https://preview.webflow.com/preview/maze-f26c8f?utm_medium=preview_link&utm_source=designer&utm_content=maze-f26c8f&preview=88e96d0206b46656022c4935ec1f91de&workflow=preview